Conection:
1) Uncheck Show Overhead Bandwidth.
2) Close all programs that are currently using your internet connection. Go to a site that can check your bandwidth and test your connection. For example, a DSL connection might get results like 1200 down/ 110 up.. Now, click on the wizard button. Select one of the three settings for Concurent Downloads. Then enter in the results of your bandwidth test into the True Download Bandwidth box and True Upload Bandwidth box. Press apply

Servers:
1) Check Remove Dead Server After __ Retries. Also set the number of retires to 1.

Statistics:
1) Increase the delay times for the things you don't montor as much. (Graphs Update delay, Statistics Tree update delay).
2) If you don't use the graphs at all.. Slide the Graphs Update delay all the way to the left for disable.
3) If you don't use the statistics at all. Slide the Statistic Tree delay all the way to the left to disable them.

Extended Settings:
1) Uncheck Verbose(additional program feedback)

Number of files downloading
Also, try not to download a huge amount of files at once. eMule has to try to handle all these files and sources at once. This can also get you banned by some servers.

Firewalls
Be aware that software firewalls usually don't like P2P's. They were not intended to have to monitor the amount of traffic a P2P generates. Although ZoneAlarm is a great firewall, it can consume a lot of memory and hog your CPU (Or even freeze your system) trying to keep up.

Hope this helps some out there.. Good luck.

Warning: I will keep this thread open for discussion.. But most likely will update the main post periodically with the good information and corrections and delete the added posts to keep this thread clean.

If your using windows XP you can save a lot of CPU resources by launching emule with this command:

Start /Low F:\Progra~1\EMULE\emule.exe

This will give emule a low processor priority, ideally you would have a batch file to avoid having to type this out every time.

Decreasing the CPU priority will not save any CPU resources for you, it will just make other programs more responsive. The bad side effect is that if any other program will decide to eat 100% of CPU time for a few seconds (while running with Normal priority), eMule will drop some or all downloads, because it doesn't have the CPU power to process these downloads.

i've a ques' about it....
if i will down the emule cpu usage the preformence of the emule will go down to?
i mean dose the download and the upload become weaker?

As I said above, this will adversely affect eMule's performance if you run some CPU-hungry application, such as archiver, mp3 encoder, movie player, 3d game, web-site with flash, etc. If such application takes all CPU time for a few seconds, eMule will find itself unable to handle all connections and will drop some or all of them. This isn't the end of the world, though. As soon as CPU is freed, eMule will recover and start downloading again. Of course, you will lose your position in the queue and so your downloads will finish a bit later... If you don't want that, don't decrease eMule's priority. If you find that it slows down your other applications, you might want to increase their priority instead of decreasing eMule's.

A simple example. You are running eMule in the background, typing a report in MS Word, use your e-mail client and need to uncompress the attachment with WinZip. There are two options:

1) Decrease the priority of eMule to LOW and leave all others at NORMAL. Then when you start unpacking a large file, eMule may not have enough CPU and drop some connections. Bad.
2) Increase the priority of MS Word to ABOVE NORMAL. Thus the program you spend most time in will be the most responsive. It is also unlikely yo take over all CPU power and so will not harm eMule. This time, when you start unpacking the file in WinZip, both WinZip and eMule will have normal priority and so will share the CPU time. The file will unpack for a few seconds longer, but eMule will not drop any connections. Good.

Hm, it's true, I share 25000 files (180 gb), and I can't store it in archives. But if I remove them from share, my rating will fall down!
I frequently leave my PC and can't follow the process of download, maybe I can do this automatelly?

Absolutely useless. there is no server that allows so much shared files. Max hard limit is set to 10000.
You don't need to do anything to keep downloading files, just let eMule running
Your rate do not depends on number of files shared but on data uploaded.